In making use of the so-called hollow, it is necessary to set the rivet by use of a rivet gun. While such rivet guns were originally purely mechanical in nature and operated by the use of the mechanical advantage obtained with a long pair of handles, the advantages of the use of hydraulic actuation has always appealed to the designers of such guns. The actual advantages of a hydraulic rivet gun have been difficult to obtain, however, because of the added complexity and cost of such guns, as well as the danger inherent in a hydraulic system. Careful design and improved manufacturing techniques have recently lowered the cost of a hydraulic rivet gun and have removed some of the inherent dangers. An example of a rivet gun of this type is shown in the patent of LaPointe U.S. Pat. No. 3,713,321 which issued Jan. 30, 1973. While the construction shown and described in that patent provides an adequate hydraulic rivet gun, it, nevertheless, suffers from some disabilities. The fact that the mandrel jaw and the hydraulic piston operate along spaced-parallel lines, for instance, can cause a binding force couple in the mechanism. It is also possible to pinch one's finger between the mandrel jaw and the rivet anvil at the nose. It is also difficult to operate if the rivet is located in a narrow recess. There is also the possibility of a user raising the hydraulic pressure to a dangerous level. These and other difficulties experienced with the prior art devices have been obviated by the present invention.
It is, therefore, an outstanding object of the invention to provide a rivet gun in which the moving mechanisms for pulling the mandrel of the rivet are located on the interior of the gun and cannot injure the user.
Another object of this invention is the provision of a rivet gun of the hydraulic type in which it is impossible to raise the hydraulic pressure to a dangerous level.
A further object of the present invention is the provision of a rivet gun having a very narrow operating nose that will permit access to a rivet located in a narrow recess.
It is another object of the instant invention to provide a rivet gun operated by a hydraulic piston in which all of the mandrel-drawing forces are in alignment, so that a binding force-couple does not exist.
A still further object of the invention is the provision of a rivet gun of the hydraulic type having a housing which can be manufactured inexpensively on conventional machine tools without the use of special castings.
It is a further object of the invention to provide a hydraulic rivet gun which is simple in construction, which is inexpensive to manufacture, and which is capable of a long life of useful service with a minimum of maintenance.
It is a further object of the invention to provide a hydraulic rivet gun which can be refilled by the user, since all hydraulic devices have some oil loss.
It is a further object of the invention to provide a hydraulic rivet gun which can be cleaned and repaired or grippers replaced with a minimum of effort.
With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.